1. Field of the Invention
The present invention relates to a still-picture imaging apparatus suitable for use with, e.g., an electronic still video camera.
2. Related Background Art
Human eyes have an adaptability to recognize a color of a white subject as white even when the light with which a field is irradiated changes. Contrastingly, for instance, in an electronic still video camera, if the irradiation light ambient to the field changes, the color also changes. Then, it is required that a white-balance be adjusted.
FIG. 4 shows processing in a conventional electronic still video camera. This processing starts with bringing a release button (unillustrated) of the electronic still video camera into a half-pushed state. Then, photometry is conducted in step S1. That is, a brightness of a field is detected. Next in step S2, a color measuring process is performed; i.e., a color temperature ambient to the field is measured. After effecting these two processes, the action proceeds to step S3. Whether or not the release button is finally turned ON (the release button is full-pushed) is judged.
When the release button is not yet full-pushed, the action proceeds to step S4. Whether or not the half-pushed state is kept is judged. If the half-pushed state is kept, the action goes back to step S1. The actions after step S1 are repeatedly executed. In step S4, if the half-pushed state is canceled, the action further proceeds to step S5. In step S5, if is judged whether or not a predetermined time (e.g., 16 seconds) has elapsed since the half-pushed state was canceled. Then, if the predetermined time has not yet passed, the action returns to step S1. Namely, even when the half-pushed state is canceled, the half-pushed state is substantially held for 16 seconds. In step S5, if the predetermined time has elapsed, the action is ended.
In step S3, if the release button is judged to be full-pushed, the action proceeds to step S6. The AE control is performed corresponding to a photometric result obtained in step S1. That is, an aperture and a shutter speed are set to predetermined values, and an exposure action is executed. The action next proceeds to step S7, wherein the white-balance is controlled. To be more specific, the white balance is adjusted corresponding to the color measured result given in step S2. Thereafter, the action goes to step S8 where imaging process is executed, and the data read from an image sensing device (not shown) such as a CCD are converted into video signals. Then, the action further proceeds to step S9, wherein the video data are recorded on a video floppy disk (magnetic disk).
The conventional apparatus is constructed with a flash device which illuminates the field with a flash of light. In this apparatus, a memory previously stores items of white-balance adjusting data for adjusting the white-balance in the case of employing the flash device. The white-balance is adjusted corresponding to the data stored in this memory when using the flash device.
In the conventional apparatus, as explained above, when half-pushing the release button, the photometric and color measuring actions are repeated. This results in an increase consumption of the electric power. Consequently, there arises a problem in that the battery is quickly consumed particularly in an apparatus of such a type that the color is measured by use of an imaging portion, the electric power consumed during the color measurement becomes remarkably larger than in the case of providing a color measuring element for an exclusive use. The consumption of the electric power is large enough not to be ignorable.
Further, according to the conventional apparatus, the white-balance is adjusted corresponding to the data stored beforehand in the memory in the case of using the flash device. In practice, however, color temperature differs among different types of flash devices. This therefore leads to such a problem that the white-balance is hard to adjust accurately. Especially in the case of taking a shot by employing the flash device when the external light is bright, it is difficult to properly adjust the white-balance.
Still further, according to the conventional apparatus, even when immediately brought into the full-pushed state subsequent to the half-pushed state, a judgement of being in the full-pushed state is made after completing the photometric and color measuring actions. It is thus impossible to take a shot quickly, and the photographer may therefore be unable to capture a brief exposure opportunity.